1. Field of the Invention
The present invention relates to a method and apparatus for ensuring proper positioning of an electronic component in a system for mounting the electronic component on a circuit board.
2. Description of Related Art
In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
As used herein, the term xe2x80x9ccomponent position correctingxe2x80x9d refers to correcting both the angular orientation of a component as well as the X-Y positioning of the component. Of course, in some cases only one of the angular orientation of the component or the X-Y positioning of the component will require adjustment.
Many types of equipment exist today for mounting electronic components on a circuit board, such as a printed circuit board. One such type of equipment includes a pick and place head that has one or more pick-up heads mounted thereon. Each pick-up head includes a spindle. At one end of the spindle is located a device for picking up the component. Such pick-up devices might include a vacuum nozzle or some other type of mechanical grabbing system. At the other end of the spindle is some type of actuating mechanism. The actuating mechanism moves the spindle from a retracted position to an extended position. In operation, the pick-up head is moved to a pick-up position above the component to be picked-up. When the pick-up head is in the pick-up position, the actuating mechanism is actuated so as to extend the spindle so that the pick-up device contacts and grabs the component. The actuating mechanism then moves the spindle to its retracted position so that the selected component may be withdrawn from the surface on which it rests. After the spindle is retracted, the pick-up head can be moved to another location so that the component can be placed at its intended location.
Due to the increased miniaturization of the components, and the miniaturization of the contact points on each component, it is important to ensure that the component is properly positioned before it is deposited at its intended location. Accordingly, at some point between the pick-up and the depositing of the component, the pick-up head must interact with a positioning system to ensure the proper positioning of the component.
In the past, such positioning may have been accomplished with a mechanical process in which the component was literally moved with respect to the pick-up head so that the component is properly positioned with respect to the pick-up head. More recently, the positioning is effected with a visual inspection system. Specifically, at some point after the component has been picked up by the pick-up head, the spindle is moved to a location adjacent a camera or imaging system. If it is determined that the component is angularly misaligned with respect to its intended placement, a system may be used to rotate the spindle to ensure proper angular orientation of the component.
On the other hand, if it is determined that the component is misaligned on the pick-up head with respect to X, Y positioning, the extent of misalignment is noted, and the pick-up head is moved accordingly when delivering the component to the intended location. Specifically, a control system notes the exact location of the component with respect to the pick-up head, and uses this information to properly place the component at the intended location.
After the component is grabbed by the pick-up head, the spindle is retracted so that the pick-up head can be moved without contacting other components. Some prior art systems, particularly those which include the vision system camera on the pick and place head, have performed the positioning analysis when the spindle is in a retracted position. However, when the component is deposited at the intended location, the spindle is extended. An inherent feature of the spindle assemblies is that when the spindle moves from the retracted position to the extended position, some shifting of the spindle and/or pick-up nozzle may occur. In other words, it is difficult to make a spindle assembly that is so precise in operation that there is no change in position of the pick-up nozzle as the spindle moves from the retracted position to the extended position, and vice versa.
Thus, in the above-mentioned prior art systems, even if the positioning of the component is exactly accomplished, as the spindle moves from the retracted position to the extended position, some shifting of the component may occur due to errors in the spindle movement. Because the positioning was effected when the spindle was in the retracted position, the changes in positioning of the component as the spindle moves from the retracted position to the extended position cannot be easily anticipated or compensated. Accordingly, such systems may result in inexact placement of the component, even though precise positioning was initially performed.
Some systems utilize a preprocessing analysis to calibrate the spindles. In such a system, the pick-up head is run through a complete cycle, wherein a vision system monitors each spindle as it moves from a retracted position to an extended position. The vision system monitors the extent of wobble or misalignment that occurs with regard to each spindle as it moves from the retracted position to an extended position, and records this information. Then, during routine processing, the recorded information concerning the wobble or misalignment of the spindle, is used to adjust each spindle during processing to minimize the extent of misalignment as the spindle moves from the retracted position to an extended position.
However, such a system may not provide enough precision or accuracy for modern needs. Accordingly, a more precise system is necessary if higher levels of precision are desired.
It is an object of the present invention to provide a system that is fast and efficient for positioning each component as it is deposited at its intended location.
It is also an object of the present invention to provide a system that is able to properly position a component with respect to its intended location, while taking into account any eccentricity or irregularities caused by movement of the spindle as the spindle moves from its retracted position to its extended position.
According to the present invention, one embodiment of a component pick and place head includes a frame; a pick-up head mounted on the frame; the pick-up head being movable from a first position in which a component is picked-up by the pick-up head to a second position in which a position of the component that has been picked up by the pick-up head is ascertained; the pick-up head being actuatable from a retracted configuration to an extended configuration for picking up the component; a first actuator for actuating the pick-up head at the first position from the retracted configuration to the extended configuration; and a second actuator at the second position for actuating the pick-up head at the second position from the retracted configuration to the extended configuration.
According to the present invention, another embodiment of a component pick and place head includes a plurality of nozzles actuatable between a retracted configuration and an extended configuration; and a cam surface adjacent a travel path of the plurality of nozzles and adjacent a camera of a vision system; the cam surface arranged so as to actuate each of the plurality of nozzles to the extended configuration as the each of the plurality of nozzles is adjacent the camera of the vision system.
According to the present invention, a method of picking and placing a component includes the steps of extending a spindle on a pick-up head from a retracted position to an extended position; picking up a component with the spindle while the spindle is in the extended position; retracting the spindle to the retracted position; moving the pick-up head with the component on it to a component position ascertation position; extending the spindle to the extended position; ascertaining a position of the component at the component position ascertation position while the pick-up head and the component are at the component position ascertation position; and depositing the component at a component deposition position.